Tetrahydrocarbyl esters of pentaerythritol are known in the art and are for example used as lubricant component in e.g. turbine oils and compressor lubricants.
U.S. Pat. No. 3,526,596 of Quaker Chemical Corporation, incorporated by reference, discloses a lubricant for to be used at very high temperatures in the process of shaping and working metals while they are heated to temperatures at which they are malleable such as hot rolling. The metal can be steel, copper, brass, aluminum, magnesium and titanium. According to a preferred embodiment, the lubricant is a pentaerythritol ester of C12-C22 fatty acids. Example 2 of U.S. Pat. No. 3,526,596 discloses the tetrahydrocarbyl ester obtained from reacting oleic acid (9-octadecenoic acid) and pentaerythritol.
U.S. Pat. No. 4,178,260 of Exxon Research & Engineering Co., incorporated by reference herein, discloses lubricants for hot and cold rolling of steel and aluminum and for casting of metals, in particular aluminum. The lubricants are said to have improved roll anti-wear and friction properties. The preferred lubricants are a mixture of (i) the tetrahydrocarbyl esters of pentaerythritol and C16-C20 aliphatic monocarboxylic acids and (ii) orthophosphoric acid. Example 5 discloses pentaerythritol tetracaproate (the tetrahydrocarbyl ester of pentaerythritol and hexanoic acid; it is not explicitly disclosed that caproic acid is n-hexanoic acid) and compared to pentaerythritol tetraoleate, it shows a higher coefficient of friction thereby teaching the person skilled in the art that the tetrahydrocarbyl ester of pentaerythritol and caproic acid is less suitable for rolling and casting applications.
U.S. Pat. No. 4,362,634 of Stauffer Chemical Company, incorporated by reference herein, discloses metal working lubricants comprising about 60 to about 90 weight percent of a polyol ester derived from the esterification of an aliphatic polyol with an aliphatic carboxylic acid. The polyol has 3 to 15 carbon atoms and 3 to 8 hydroxy groups and is preferably trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol and mixtures thereof. The carboxylic acid is selected from the group consisting of aliphatic monocarboxylic acids and mixtures of aliphatic monocarboxylic acids and aliphatic dicarboxylic acids. The aliphatic monocarboxylic acid contains 4 to 18 carbon atoms and suitable examples include hexanoic acid, heptanoic acid, nonanoic acid and mixtures thereof. A mixture of aliphatic monocarboxylic acids and aliphatic dicarboxylic acids is used when increased viscosities are desired. The example discloses Basestock 810™ which according to U.S. Pat. No. 4,530,772 is a pentaerythritol ester of C7 acid crosslinked with azelaic acid.
U.S. Pat. No. 5,761,941 of Kabushiki Kaisha Kobe Seiko Sho. and Kao Corporation discloses a lubricant composition for press-forming an aluminum or aluminum alloy sheet comprising a hydrocarbon and a C10-C24 linear of branched fatty alcohol. The lubricant composition may further comprise a component (c), said component (c) being selected from the group consisting of (1) oils and fats, (2) esters of a polyol and a C12-C24 fatty acid and (3) esters having a Mw of 750 to 7500 which are obtained by reacting a C12-C24 alcohol or a C12-C24 fatty acid with residual carboxy groups or hydroxy groups, respectively, of an ester of a dimeric acid or polymeric acid of a C16-C20 fatty acid and a polyol. Example 1 discloses an Ester E which is a tetra-ester of pentaerythritol and hydrogenated coconut oil fatty acid which consists for the major part of C12-C18 acids and an ester D which is obtained by condensing an ester of dimeric oleic acid and ethylene glycol with stearyl alcohol.
US 2004/0116308 of Nippon Mitsubishi Oil Corp. discloses oils for cutting and grinding comprising an ester which may be derived from monohydric or polyhydric alcohols and monobasic and polybasic acids. Preferred are esters from polyhydric alcohols and monobasic acids, e.g. the triester of neopentyl glycol and oleic acid, the triester of trimethylolpropane and oleic acid, the tetraester of trimethylolpropane and a mixture of n-hexanoic acid, n-octanoic acid and n-decanoic acid (molar ratio of 7;59;34) and the tetraester of pentaerythritol and n-octanoic acid.
JP 2000073079 discloses a metal working fluid comprising a triester of glycerol and C8-C12 acids.
U.S. Pat. No. 6,462,001 of Unichema discloses complex esters which may be used for metal working and metal rolling applications. The complex esters are made by condensing polyfunctional alcohols, polyfunctional acids and a chain stopper, the chain stopper being either a mono fatty acid or a mono fatty alcohol.
EP 1.529.828 of Malaysian Palm Oil Board discloses the tetraester of pentaerythritol and caprylic acid and the tetraester of capric acid.
JP A 4117494, JP A 4117495 and JP A 4118101 of Nihon Kueeka Kemikaru KK, incorporated by reference herein, disclose a rolling oil additive comprising a lubricating component, e.g. a polyhydric alcohol ester of a higher fatty acid, which has a viscosity of 80 cSt or more at 40° C.
RU 2.163.625 C2, incorporated by reference herein, discloses a lubricant for hot rolling comprising an ester of “pentaerythrite” (this term is an equivalent of pentaerythritol) and synthetic C5-C9 fatty acids. However, the structure of either the esters or the fatty acids is not disclosed.
WO 2005/017078 of ICI, Ltd., relates to a water soluble rolling oil composition for use in cold steel rolling applications comprising a partial polyol ester having a OH-value of 20-50 mg KOH/g and a level of unsaturation of 0.01-8% by weight. The partial polyol ester is derived from the reaction between a polyhydric alcohol, e.g. pentaerythritol, and monocarboxylic acids, wherein part of these monocarboxylic acids is unsaturated. Tetrahydrocarbyl esters of pentaerythritol are, however, not disclosed.
It is generally known that metal processing lubricant compositions have to meet many requirements including good friction properties over a wide range of film thicknesses, good compatibility with other lubricating additives, excellent compatibility with aqueous systems, good evaporation and annealing characteristics, a high corrosive and oxidation stability, in particular at elevated temperatures, a relatively low pour point, low foam formation, iron fines handling, sheet- and mill cleanliness and the like: see for example U.S. Pat. No. 4,746,448, U.S. Pat. No. 4,885,104 and U.S. Pat. No. 4,889,648, all incorporated by reference. Although many metal processing lubricant compositions are disclosed in the prior art and are even commercialized, there remains a need within the art to provide metal processing lubricant compositions that meet those performance requirements in an improved manner and that are applicable under a wide range of operating conditions.